From c33058d5eb89e0513c901c5c796ad391c700c614 Mon Sep 17 00:00:00 2001
From: null <koga.industries@gmail.com>
Date: Sat, 20 Jun 2026 23:14:47 -0500
Subject: [PATCH] fix(firestore): harden isImmutable helper to reject non-list
 args

---
 firestore.rules | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/firestore.rules b/firestore.rules
index 383afb0c..9203835f 100644
--- a/firestore.rules
+++ b/firestore.rules
@@ -34,7 +34,8 @@ service cloud.firestore {
     // must only be performed server-side is denied for all direct client writes.
 
     function isImmutable(fields) {
-      return !request.resource.data.diff(resource.data).affectedKeys().hasAny(fields);
+      return fields is list
+        && !request.resource.data.diff(resource.data).affectedKeys().hasAny(fields);
     }
 
     function isValidSwipeAction(action) {